The present invention relates generally to user input and display devices for controlling a range or the like and, more particularly, to ON/OFF switch arrangements for touch control bar graph devices such as are disclosed in the applications cross referenced above.
In the above-mentioned Welch, Serrano and Chen and the Serrano applications, devices are disclosed which advantageously and effectively combine touch switch user-input technology and bar graph display output technology to provide simple and readily understandable input/output devices herein referred to as touch control bar graph devices. More specifically, the display portion of a touch control bar graph device is a bar graph display which continuously and graphically represents a selected value, such as a range heat setting. The input portion is an array of touch-sensitive areas superimposed over the bar graph, permitting convenient changes to the setting with immediate reinforcing visual feedback to the user. In operation, the end of the bar graph display "follows" the tip of the user's finger in a unique and pleasing manner. Such touch control bar graph devices are a significant improvement over previously employed input/output devices for electronically controlled apparatus such as appliances, particularly when "human engineering" and user acceptability considerations are taken into account. The devices are readily understandable and permit the construction of unintimidating control panels which a person may use with confidence.
The previously disclosed touch control bar graph devices activate the load device, for example a range surface unit, whenever touched. Additionally, there is a separate "OFF" touch pad which turns off the touch control bar graph device and the load when touched.
In certain applications, and in particular in a control for a range surface unit, safety considerations are of utmost priority. In a range cooktop, the possibility of a surface heating unit being energized accidentally should be minimized. At the same time, interference with convenient operation of the appliance should be minimized to the extent possible consistent with safety considerations.
An Underwriters Laboratory requirement has addressed this particular concern. Specifically, in UL 858 pertaining to "Household Electric Ranges," Section 43 deals with "Unintentional Operation of Surface-Unit Controls."
UL Paragraph 43.1 requires, "The control for a surface unit shall require a minimum of two operations to activate the surface unit." In conventional, non-electronic ranges employing rotary switches and controls, the requirement of paragraph 43.1 is typically met by a switch having a push and a turn or a pull and a turn operating sequence. This particular solution is generally approved in paragraph 43.3 of the UL requirement. Lastly, paragraph 43.2 requires, "Only one operation shall be required to turn a surface unit off."
One example of a prior art electronic range including touch control input devices is disclosed in U.S. Pat. No. 3,819,906 issued to Gould, Jr. The Gould, Jr. range satisfies the UL "two operation" requirement by having "address pads," located near the right side of the control panel, for the individual surface cooking units. Separate "setting pads" numbered 0 through 9 are located near the center of the control panel and shared by all four surface units. Each of the "setting pads" corresponds to a particular heat value. To activate a heating unit of the Gould, Jr. range, a user first touches one of the "address pads" and then touches one of the setting pads.